Since eyeglasses are commonly misplaced, those who wear them, whether for vision enhancement or blocking sunlight, are repeatedly forced to search for those eyeglasses at particularly inconvenient moments. For example, when driving a car, a change of direction may result in the driver facing the sun. In such a situation, the driver will want to conveniently locate and secure sunglasses while keeping a hand on the driver's wheel and his or her eyes on the road. Similarly, if one is driving or sailing a boat, one would like to secure one's eyeglasses conveniently while keeping one's eyes on the water.
In either context, the person is forced to divert attention from the task at hand and search for the eyeglasses. The search is inconvenient, if not dangerous. Furthermore, if and when found, the eyeglasses are commonly in a position which allows them to be scratched or otherwise damaged.